1. Field of the Invention
The present invention relates to an electrophotographic photoreceptor. More particularly, it relates to an electrophotographic photoreceptor which is excellent in surface smoothness, abrasion resistance and electrical properties.
2. Discussion of Background
In recent years, electrophotography has been widely used and applied not only in the field of copying machines but also in the field of various printers, by virtue of instantaneous and high quality of images thereby obtainable. With respect to a photoreceptor which is essential to the electrophotography, an inorganic photoconductor such as selenium, an arsenic-selenium alloy, cadmium sulfide or zinc oxide has heretofore been used as its photoconductive material, and recently, a photoreceptor employing an organic photoconductive material has been developed which has a merit such that the layer-forming is easy without environmental pollution, and the production is easy.
Among organic photoreceptors, a so-called laminate type photoreceptor having a charge generation layer and a charge transport layer laminated, has been devised and is being intensively studied.
The laminated type photoreceptor has a possibility that it will be employed as the main photoreceptor, since a highly sensitive photoreceptor can be obtained by a combination of a highly efficient charge generation material and a highly efficient charge transport material, the range for selection of materials is wide and a highly safe photoreceptor can be obtained, and since the coating productivity is high and it is relatively advantageous also from the viewpoint of costs. Accordingly, it is actively being developed.
However, conventional organic laminate type photoreceptors have been inadequate in the physical strength of the surface of the photoreceptors, whereby printing resistance has been practically limited, although they exhibit adequate performance in the electrical properties such as the sensitivity and electrification properties. It is the mechanical properties of the charge transport layer in a laminate type photoreceptor that substantially determines the physical strength of the surface of the photoreceptor.
In order to increase the mechanical strength, it has been proposed heretofore, for example, to provide an overcoating layer (JP-A-61-72256) or to use a binder polymer having a high abrasion resistance (JP-A-63-148263 and JP-A-3-221962). However, such proposals have been inadequate in the intended effects or have had a problem that they tend to adversely affect the properties such as electrical properties.
Further, in recent years, along with improvement of the image quality, a photoreceptor having excellent surface smoothness has been desired. In order to improve the surface smoothness, it has been proposed, for example, to employ a polysiloxane block copolymer as a binder (JP-A-61-132954 and JP-A-2-240655), to employ a polysiloxane terminal compound having a low molecular weight (JP-A-7-261440), or to employ a fluorine atom-containing polycarbonate (JP-A-5-306335, JP-A-6-32884, and JP-A-6-282094). However, such proposals have been inadequate in the intended effects or have had a problem that they tend to adversely affect the electrical properties or the printing resistance.